Patent Application
20200263665
The present disclosure relates in general to wind turbine, and more particularly to systems and methods for protecting wind turbines from flutter during high wind speeds.
Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a nacelle fixed atop a tower, a generator and a gearbox housed with the nacelle, and a rotor configured with the nacelle having a rotatable hub with one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
The rotor blades generally include a suction side shell and a pressure side shell secured together at bond lines along the leading and trailing edges of the blade. Further, the pressure and suction shells are relatively lightweight and have structural properties (e.g., stiffness, buckling resistance and strength) which are not configured to withstand the bending moments and other loads exerted on the rotor blade during operation. Thus, to increase the stiffness, buckling resistance, and strength of the rotor blade, the body shell is typically reinforced using one or more structural components (e.g. opposing spar caps with a shear web configured therebetween) that engage the inner pressure and suction side surfaces of the shell halves. The spar caps and/or shear web may be constructed of various materials, including but not limited to glass fiber laminate composites and/or carbon fiber laminate composites.
In recent years, wind turbines for wind power generation have increased in size to achieve improvement in power generation efficiency and to increase the amount of power generation. Along with the increase in size of wind turbines for wind power generation, wind turbine rotor blades have also increased in size. With this increased size, the wind turbine structure as well as the rotor blades can also experience increased loading.
For example, high wind speed zones (e.g. hurricanes, typhoons, etc.) create challenges for large wind turbines, where the risk to the structure becomes very high, particularly when the wind turbine does not have any structural reinforcement. One such risk is flutter phenomenon, which generally refers to the dynamic instability of an elastic structure in a fluid flow, caused by positive feedback between the body's deflection and the force exerted by the fluid flow.
Thus, to minimize the negative effects mentioned herein, it would be advantageous for the wind turbine to include a control logic that protects wind turbines from flutter during high wind speeds. Accordingly, the present disclosure is directed to improved systems and methods that reduce or eliminate flutter by modifying blade pitch angle of the wind turbine.
Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention
In one aspect, the present disclosure is directed to a method for protecting an idling wind turbine power system from damage during loss of grid power. The wind turbine power system has a plurality of rotor blades. The method includes monitoring an incoming wind direction at the wind turbine power system. When the incoming wind direction is changing at a predetermined attack angle, the method also includes rotating at least one of the rotor blades of the wind turbine power system to a pitch angle that is offset from a feather position by a predetermined number of degrees to reduce and/or eliminate flutter phenomenon from occurring.
In one embodiment, the method may also include determining at least one of a rotor position or a rotor orientation of the wind turbine power system and rotating at least one of the rotor blades of the wind turbine power system to the pitch angle that is offset from the feather position by the predetermined number of degrees when the rotor position and/or the rotor orientation are indicative of the flutter phenomenon occurring.
In another embodiment, the method may further include yawing the nacelle of the wind turbine approximately 180 degrees away from the incoming wind direction when the incoming wind direction is changing at the predetermined attack angle. In certain embodiments, the predetermined number of degrees may include, for example, less than about 10 degrees.
In additional embodiments, rotating at least one of the rotor blades to the pitch angle that is offset from a feather position by the predetermined number of degrees may include rotating each of the plurality of rotor blades by the same number of degrees. In alternative embodiments, rotating at least one of the rotor blades to the pitch angle that is offset from a feather position by the predetermined number of degrees may include rotating each of the plurality of rotor blades by a different number of degrees.
In particular embodiments, the feather position may include a position in which a chord of the rotor blade is approximately inline with the incoming wind direction at stand still or minimal rotation.
In yet another embodiment, the method may include utilizing backup energy stored in the wind turbine power system for powering one or more wind turbine components during the loss of grid power. In such embodiments, the wind turbine power system may include at least one energy storage device for storing the backup energy. In addition, the wind turbine component(s) may include one or more pitch drive mechanisms, one or more yaw drive mechanisms, a brake, a main controller, and/or one or more electrical components of the wind turbine power system.
In further embodiments, if the main controller of the wind turbine power system is offline due to the loss of grid power, the energy storage device is configured to power operation of the wind turbine power system without interruption.
In another aspect, the present disclosure is directed to a backup control system for protecting an idling wind turbine power system from damage during loss of grid power. The backup control system includes a pitch control system having an auxiliary power supply and a plurality of pitch drive mechanisms communicatively coupled to the auxiliary power supply via a communication link. As such, during the loss of grid power, the auxiliary power supply powers the pitch control system to implement a control scheme for the wind turbine power system. The control scheme includes monitoring an incoming wind direction at the wind turbine power system. When the incoming wind direction is changing at a predetermined attack angle, the control scheme includes rotating at least one of the plurality of rotor blades of the wind turbine power system to a pitch angle that is offset from a feather position by a predetermined number of degrees to reduce and/or eliminate flutter phenomenon from occurring. It should be understood that the method may also include any of the steps and/or features as described herein.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Referring now to the drawings,
The wind turbine 10 may also include a wind turbine controller 26 centralized within the nacelle 16. For example, as shown, the turbine controller 26 is located in the top box cabinet 48 (
Referring now to
The wind turbine 10 may also a yaw drive mechanism 40 configured to change the angle of the nacelle 16 relative to the wind (e.g., by engaging a yaw bearing 42 of the wind turbine 10 that is arranged between the nacelle 16 and the tower 12 of the wind turbine 10). Further, each yaw drive mechanism 40 may include a yaw drive motor 44 (e.g., any suitable electric motor), a yaw drive gearbox 45, and a yaw drive pinion 46. In such embodiments, the yaw drive motor 44 may be coupled to the yaw drive gearbox 45 so that the yaw drive motor 44 imparts mechanical force to the yaw drive gearbox 45. Similarly, the yaw drive gearbox 45 may be coupled to the yaw drive pinion 46 for rotation therewith. The yaw drive pinion 46 may, in turn, be in rotational engagement with the yaw bearing 42 coupled between the tower 12 and the nacelle 16 such that rotation of the yaw drive pinion 46 causes rotation of the yaw bearing 42. Thus, in such embodiments, rotation of the yaw drive motor 44 drives the yaw drive gearbox 45 and the yaw drive pinion 46, thereby rotating the yaw bearing 42 and the nacelle 16 about the yaw axis 43. Similarly, the wind turbine 10 may include pitch control system 35 having one or more pitch adjustment mechanisms 32 communicatively coupled to the wind turbine controller 26, with each pitch adjustment mechanism(s) 32 being configured to rotate the pitch bearing 47 and thus the individual rotor blade(s) 22 about the pitch axis 28.
In addition, the wind turbine 10 may also include one or more sensors 52 for monitoring various wind conditions of the wind turbine 10. For example, the incoming wind direction 66, wind speed, or any other suitable wind condition near of the wind turbine 10 may be measured, such as through use of a suitable weather sensor 52. Suitable weather sensors 52 include, for example, Light Detection and Ranging (“LIDAR”) devices, Sonic Detection and Ranging (“SODAR”) devices, anemometers, wind vanes, barometers, radar devices (such as Doppler radar devices) or any other sensing device which can provide wind directional information now known or later developed in the art.
Referring now to
As used herein, the term “processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s) 60 may generally comprise memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements.
Such memory device(s) 60 may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s) 58, configure the controller 26 to perform various functions as described herein. Additionally, the controller 26 may also include a communications interface 62 to facilitate communications between the controller 26 and the various components of the wind turbine 10. An interface can include one or more circuits, terminals, pins, contacts, conductors, or other components for sending and receiving control signals. Moreover, the controller 26 may include a sensor interface 64 (e.g., one or more analog-to-digital converters) to permit signals transmitted from the sensors to be converted into signals that can be understood and processed by the processors 58.
Referring now to
More specifically, as shown in the illustrated embodiment, the control system 100 includes a top box distributed I/O module 104, a downtower distributed I/O module 106, and a tower distributed I/O module 108. Further, as shown, each of the distributed I/O modules 104, 106, 108 are connected to the main turbine controller 26 via a plurality of communication link 92 for command and monitoring. It should be understood that the communications links 92 as described herein may include any suitable communication medium for transmitting the signals. For instance, the communications links 92 may include any number of wired or wireless links, including communication via one or more Ethernet connections, fiber optic connections, network buses, power lines, conductors, or circuits for transmitting information wirelessly. Further, signals may be communicated over the communications links 92 using any suitable communication protocol, such as a serial communication protocol, broadband over power line protocol, wireless communication protocol, or other suitable protocol.
Thus, during normal operation, the turbine controller 26 is configured to receive information from the input modules and send information to output modules. The inputs and outputs can be either analog signals which are continuously changing or discrete signals. More specifically, in certain embodiments, the top box distributed I/O module 104 is configured to provide I/O to the turbine controller 26 so as to control uptower components of the wind turbine 10, e.g. the yaw drive mechanisms 40 and/or the pitch drive mechanisms 32. Similarly, the downtower distributed I/O module 106 is configured to provide I/O to the turbine controller 26 so as to control the downtower electrical assembly, e.g. transformers, etc. The tower distributed I/O module 108 is configured to provide I/O to the tower components as described herein. In addition, the control system 100 may include more or less distributed I/O modules than those depicted in
Referring still to
The control system 100 may further include a braking unit 76 coupled to the variable frequency drive 74. More specifically, as shown in the illustrated embodiment, the braking unit 76 may include a brake chopper 78 coupled to the variable frequency drive 74 and at least two dynamic brake resistors 80, 82 coupled to the brake chopper 78. As such, the multiple dynamic brake resistors 80, 82 provide redundancy to the braking unit 76 in the event of a resistor failure.
Further, as shown, the control system 100 includes at least two energy storage devices 84, 86 coupled to the braking unit 76. More specifically, as shown, each of the energy storage device(s) 84, 86 may include at least two battery units 85, 87 coupled to at least two battery chargers 88, 89 via a fuse 90. In other words, the battery units 85, 87 and/or battery chargers 88, 89 are designed to operate in a load-sharing configuration, with each of the battery units 85, 87 and/or battery chargers 88, 89 capable of taking the complete load. Further, the fuse 90 described herein provides DC fuse protection at the output of battery unit(s) 85, 87, particularly for overload and arc flash protection against short circuits.
As mentioned, the control system 100 also includes the yaw drive mechanisms 40 (including, at least, the yaw drive motor 44 and the yaw bearing 42) and the pitch drive mechanisms 32 described herein that are communicatively coupled to the auxiliary power supply 72 and the main controller 26 via one or more communication links 92. More specifically, as shown, each of the yaw drive mechanisms 40 includes a yaw power control device (e.g. yaw variable frequency drive 75). For example, in certain embodiments, the yaw variable frequency drives 75 may correspond to four-quad front end converters that provide back-to-back AC DC bridges to enable energy flow in both the directions with a common DC bus. In addition, as shown, the control system 100 may include a multiple-winding transformer 77 to facilitate the bidirectional energy transfer, thereby enabling the exchange of energy between all system components.
Referring still to
Referring now to
As shown at (202), the method 200 may include monitoring an incoming wind direction at the wind turbine power system 10. As shown at (204), the method 200 includes determining whether the wind direction is changing at a predetermined attack angle. If so, as shown at (206), the method 200 may include implementing a control scheme 208 for the wind turbine power system 100. For example, as shown at (210), the control scheme 208 may include rotating at least one of the rotor blades 22 to a pitch angle that is offset from a feather position by a predetermined number of degrees to reduce and/or eliminate flutter phenomenon from occurring. In such embodiments, the feather position described herein may include a position in which a chord of the rotor blade 22 is approximately inline with the incoming wind direction 66 at stand still or minimal rotation.
In one embodiment, as shown at (212), the control scheme 208 may also include determining a rotor position and/or a rotor orientation of the wind turbine power system 10 and rotating at least one of the rotor blades 22 to the pitch angle that is offset from the feather position by the predetermined number of degrees when the rotor position and/or the rotor orientation are indicative of the flutter phenomenon occurring. More specifically, in one embodiment, the predetermined number of degrees may be less than about 10 degrees, such as less than about 5 degrees. In such embodiments, the minuscule deviation/offset of individual blades 22 from the feather position is configured to result in drastic reductions in flutter and is possible due to the control system 100 having significant stored backup energy that is available during loss of grid power. In certain embodiments, the method 200 may include rotating each of the rotor blades 22 away from the feather position by the same number of degrees. In alternative embodiments, the method 200 may include rotating each of the rotor blades 22 away from the feather position by a different number of degrees.
In another embodiment, the method 200 may further include yawing the nacelle 16 approximately 180 degrees away from the incoming wind direction 66 when the incoming wind direction 66 is changing at the predetermined attack angle.
In several embodiments, the method 200 may also include utilizing backup energy stored in the wind turbine power system 100 for powering one or more wind turbine components during the loss of grid power. In such embodiments, as mentioned, one or more of the energy storage devices 84, 86 are configured for storing the backup energy. As such, if the main controller 26 of the wind turbine power system 100 is offline due to the loss of grid power, the energy storage devices 84, 86 are configured to power operation of the wind turbine power system 100 without interruption.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
